Acid-base properties of nicotinamide in aqueous-acetone solutions

The constants of protonation of nicotinamide in aqueous-acetone solvents of various compositions were determined by potentiometric titration at 298 K and ionic strength of 0.25 (NaC1O(4)). It was found that the increase in the concentration of acetone in the binary solvent from 0.0 to 0.45 mole fractions results in a decrease in the protonation constant. The effect of a change in the degree of solvation of the reagents in the aqueous-acetone solvent on the protonation equilibrium of nicotinamide was considered. As the concentration of acetone in the binary solvent increases, the protonation constant decreases due to the growth of the degree of solvation of the proton.